UC San Diego

The realization of the environmental and economic impact that occurs from the release of carbon dioxide derived from fossil fuel has spurred technologies focused on renewable alternative energy production. The production of liquid based biofuel from microalgae has been one of the proposed solutions due to microalgae’s high productivity per acre of land, its ability to accumulate large amounts of the precursor to biofuel, triacylglycerol, and its dependence on carbon dioxide, allowing for sequestration of anthropogenic CO2 from the atmosphere. The promise of microalgae as a feedstock for the large-scale commercial production of biofuel is impressive, however, there are significant advances in productivity still needed in order to make the solution economically and industrially feasible. For instance, the mechanisms that control triacylglycerol accumulation and cellular division in microalgae are still largely unknown. Moreover, most studies on these processes have been focused on model organisms for basic research, not on species that are industrially relevant. The immense diversity of algae as well as their complex evolutionary history indicates that molecular mechanisms controlling primary metabolism are not necessarily ubiquitous. Therefore, elucidation of carbon metabolism in a candidate species for commercial production is key for the biological comprehension within algal biofuel production. The main objective of this dissertation was to characterize primary carbon metabolism in the diatom Cyclotella cryptica, a species of microalgae with promise for large-scale industrial production. Chapter 1 investigated the neutral lipid accumulation response of C. cryptica through the comparison of two macronutrient starvation using imaging flow cytometry. Chapters 2 and 3 applied high-throughput sequencing technologies to identify the molecular and metabolic controls of triacylglycerol accumulation. The data presented in this dissertation will hopefully move this species and others closer to the economic feasibility of commercial scale algal biofuel by characterizing key areas of metabolism pertinent to triacylglycerol formation, providing genomic datasets necessary for the development of genetic engineering tools, and establishing a model for primary carbon metabolism in an industrially relevant species.